2.1.4 Triggering From Properties

In most cases, programs and server operations are triggered (i.e. caused to run or execute) by typing a command. However, they can also be triggered from a number of protected properties: all message props (_/de, _/sc, etc.), plus _connect, _oconnect, _disconnect, _odisconnect, _arrive, _oarrive, _depart, _odepart, and _listen.

Performing any of the actions implied by these property names sends information to the server and (if the property is set correctly) causes messages to be displayed, an MPI string to be parsed, or a program to run. For example, if you set a _connect prop on your character to trigger a certain program, the program will run each time you connect; if you put an MPI string in your _/de prop, it will be parsed each time someone looks at you. The server searches up the environment tree (see Section 2.2) for triggering props. For example, if _connect prop that triggers a program is set on your character, the program will run each time you connect. If it's set on a room, the program will run each time someone connects in that room. If it's set on the global parent room (#0), the program will run each time someone connects anywhere on the MUCK.

The manner in which the props are set differs depending on which prop it is (the _/ directory is handled differently than the others, such a _connect or _listen) and on what the intended result is (messages are handled differently than MPI, which is handled differently than program calls).

To cause a message to be displayed by a _/ prop (_/de, _/sc, etc), simply set the message as a string, with @set or the specific server command. @o- messages such as @osucc, @ofail, and @odrop are prepended with the name of the triggering player (or other object type).

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> @desc out=A simple wooden door.
  Message set.
> look out
  A simple wooden door.

> @succ out=You decide to go outside for a bit...
  Message set.
> out
  You decide to go outsides for a bit...

> @set out=_/sc:You head outside.
  Property set.
> out
  You head outside.
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MPI strings in _/ props will be parsed automatically.

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> @desc watch=You glance at your watch. The time is {time}.
  look watch
  You glance at your watch. The time is 01:44:31.
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To trigger a MUF program from a _/ prop, preceed the dbref of the program with an @ at-mark. For example, let's assume the dbref of the `Obvious Exits' program is #123:

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> @succ here=@#123
  Message set.
> look here
  Messy Room(#545RJ)
  Boy, this place is a mess!
  Obvious Exits:
      Out <O>
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The other triggering props (_arrive, _oconnect, etc) are handled slightly differently. Simple strings cause no result, MPI must be preceeded with an & ampersand in order to be parsed, and MUF programs can be called with just a string indicating the dbref.

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> @set me=_connect:555
  Property set.
> @set me=_arrive:&{null:{otell:waltzes in.}}
  Property set.
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These triggers can be set up as a propdir rather than a single prop, in order to trigger multiple results from the same action. For example, the following settings would trigger both programs #581 and #555 each time someone connects in the room. The propdirs are evaluated in alphabetical order, so #581 would execute first. (Other than determining alphabetical order, the prop names following the first / slash mark have no effect: they can be whatever you like.)

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> @set here=_connect/desc-check:#581
  Property set.
> @set here=_connect/my-wwf:#555
  Property set.
====================================


The _listen is triggered by any activity. As such, it is both very useful and very easily abused. Permissions safeguards are coded into the server for _listen: the only result that can be triggered is execution of a program; the program must be set Link_OK and have a Mucker level equal to or higher than a level set by the MUCK administrators. Usually this parameter is set to 3 or 4 (M4 is `wizard'). `Bot programs and automatic `noise' or `event' programs are common examples. The prop is set simply by putting the dbref of the program to run in the property value.

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> @find noises
  noises.muf(#812FLM3)
  ***End of List***
  1 objects found.
> @set here=_listen/noise:812
  Property set.
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